Purchase this article with an account.
Arne Ohlendorf, Frank Schaeffel; Effects Of Astigmatic Defocus On Visual Acuity, Contrast Sensitivity And Contrast Adaptation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1898.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine the effects of the axis of imposed astigmatic refractive errors on visual acuity, contrast sensitivity, and contrast adaptation.
Experiment 1: the effects of imposed positive and negative astigmatic defocus on visual acuity was tested in 9 subjects (mean age 27.2 ± 1.8 years) at 3 different visual acuity levels (logMAR 0.0, logMAR 0.2 and logMAR 0.5) using letter charts. Experiment 2: contrast sensitivity was tested when the axes of +1D or +2D astigmatic defocus were varied at three spatial frequencies (1.5, 3 and 6 c/deg) in 10 subjects (mean age: 28.2 ± 3.6 years), using the FrACT. Experiment 3: adaptation to astigmatic defocus was studied in 10 subjects (mean age 26.7 ± 2.4 years) while the axes of astigmatism were varied. Adaptation was induced with a +3D astigmatic lens while the subjects watched a movie for 10 minutes. Visual acuity was measured before and after adaptation with letter charts.
Experiment 1: visual acuity was not dependent on the axes of imposed astigmatic defocus (positive and negative defocus, logMAR 0.0, logMAR 0.2 and logMAR 0.5, p>0.05, Tukey-Kramer Test). Experiment 2: using the FrACT, contrast sensitivity was not dependent on the axes of imposed astigmatic defocus at any of the tested spatial frequencies (neither for +1D and +2D astigmatic defocus, p> 0.05, Tukey-Kramer Test). Experiment 3: an increase in visual acuity was observed (logMAR 0.068±0.031, p<0.001, paired T-Test) after adaptation to astigmatic defocus, when the axis of astigmatism during adaptation and testing were matched. When the axes were different, adaptation did not improve visual acuity (logMAR 0.04±0.09, p=0.19, paired T-Test).
We found no effect of the orientation of the axis of astigmatism on visual acuity and contrast sensitivity, as tested with letter charts and the FrACT. We also found a meridian selective adaptation to astigmatic defocus. It was not necessary to adapt to the same visual test target - a movie worked well.
This PDF is available to Subscribers Only